This is a very interesting question and one that comes up quite often. The standard height for benchtops is 900mm from finished floor level. this has been the standard height for near on 100 years. Now, the issue is that over the last 100 years, the human race as a whole has increased in height. Even a small increase in bench height can have a huge impact on the usability of the kitchen. Have you ever stood at a sink and your back starts to ache after 5 minutes? Most of our kitchens are installed at 920mm, but some will go in higher "IF" the owners are taller

A good rule of thumb is 1m from table to a wall, to allow room for the chair to go back when the person is seated without feeling too crowded. For a thoroughfare behind a chair I would allow 1.2 - 1.5 from table to bench, the more the better.

I have a stool on the kitchen side of the island and love it. It does men you lose a cupboard to allow for the stool , and the space between the island and kitchen bench needs to be at least 1200- mine is 1400. It is great for socialising around the bench. It seems to be where we all gather- I can sit and join in, organise food, drinks easily. It works so well 2 of my friends have incorporated the idea into their kitchens.

If the island is Screw s from the inside of the cabinet. Angle brackets or L-shape channel under the timber. There are many different ways of doing it. depending on how elegant you want it to look and what material it's connected to.